A keyboard musical instrument such as an electronic piano is provided with a keyboard lid such as a fallboard to cover and protect the keyboard. The keyboard lid is generally of a type which just open and close the keyboard part of the instrument by turning the pivoted lid through a limited angle of about 100 or 120 degrees to expose or hide the keyboard. This type of keyboard lid is really useful for protecting the keyboard when it is closed, where the instrument is not in use, but is useless or rather obstructive where the instrument is being played by the performer. To mitigate the obstructiveness, a keyboard lid of a sliding shutter type was devised as shown in registered Japanese utility model publication No. 2,571,343 in which the shutter plate is slid into the instrument housing to hide the shutter plate while exposing the keyboard.
Such an instrument having a fallboard of a pivoted lid type turning through a limited angle may cause some inconveniences including the following. The fallboard will stand aslant upward at the rear end of the keyboard and obstruct the player's view ahead, so that communications between the keyboard instrument player and other instrument players may be spoiled especially in the case of an ensemble. Where speakers are provided on the rear top board of the keyboard musical instrument, as is often the case with electronic pianos, the obliquely standing fallboard to open the keyboard part will hinder the emitted sounds of the loudspeakers from reaching the player's ears, which may ruin the tone quality of the sounds perceived by the player. On the other hand, in the case of an instrument having a sliding keyboard lid such as shown in the above-referenced Japanese utility model publication, the mechanism of hiding the keyboard lid will be complicated and the instrument housing will be bulky accordingly. In either case, the keyboard lid will not play a useful role while the keyboard instrument is being played.